|
As one of the largest quantitative resources regenerative and reusable in nature, chitin was an important matter of bio-product available widely for textile process, medicine & healthcare, agriculture, environmental protection, cosmetics, etc. with high economic value and great utilizing prospects. It occurs universally in shells of shrimps and crabs, which predominate over the industrialization of these linear polysaccharides. However, there was some ignoring on insects ——the most numerous species among the whole global creatures and another plentiful supply of natural chitin aggregation. Such chitin and its derivatives from wall of insect’s body had not been fully developed for both experimental and commercial purposes. Therefore, four species of frequently-seen insects were selected for the isolation of chitin and the preparation of its derivatives in this investigation. According to the data analysis based on chitin extracted from Cryptotympana atrata (Fabricius), Oxya chinensis (Thumb.), Blaps japanensis yunnanensis Mars. and Ericerus pela Chavannes, an optimal technique of insect chitin extraction process was found, so was the best conditions for preparation of chitin derivatives such as chitosan and carboxymethylchitosan (CMC). In the isolation of insect chitin, deproteinization and deminerazation were applied in turn. It showed that concentration of NaOH and temperature & period of reaction were significant factors for the removal of proteins, samples treated with 6% NaOH at 90 ℃for 1h, 7% NaOH at 90℃for 30min, 7% NaOH at 90℃for 5h, or 7% NaOH at 90℃for 1h were the most suitable for deproteinization; and for deminerazation, concentration of HCl and period of reaction affected considerably the removal of inorganic salts, at room temperature, 0.2 mol/L HCl for 20min, 0.3 mol/L HCl for 10min, 0.2 mol/L HCl for 10min, or 0.2 mol/L HCl for 70min treatment were the most suitable for deminerazation. Chitosan was prepared from Cryptotympana atrata (Fabricius) chitin by deacetylation, which was controlled mainly with concentration of NaOH and temperature & period of reaction. With 50% NaOH treated at 120 ℃for 3h, it achieved a high degree of chitin deacetylation for a better preparation of chitosan. Carboxymethylchitosan was synthesized with chitosan and monochloroactic acid. The reaction was influenced mainly by dosage & concentration of NaOH, dosage of chloroactic acid and temperature & period of reaction. The experimental results indicated that the optimum reaction conditions were as follows: the ratio of chitosan to NaOH (in weight) was 3∶1, chloroactic acid to chitosan (in weight) was 3∶1, samples were treated with 35% NaOH at 70℃for 2h.
|